Method of making spiral conveyer-flights and the like.



No. 805,629. I PATENTED NOV. 28, 1905. 1 G. CALDWELL.

METHOD OF MAKING SPIRAL CONVEYER FLIGHTS AND THE LIKE.

APPLIGATION FILED $173.14, 1899.

UNITED STATES PATENT OFFICE,

Specification of Letters Patent.

Patented Nov. 28, 1905.

Application filed February 14, 1899. Serial No 705,505.

To all whom it may concern.-

Be it known that I, FRANKC. CALDWELL, a citizen of the United States of America, residing at Oak Park, in the county of Cook, in the State of Illinois, have invented a certain new and useful Improvementin the Method of Making Spiral Conveyer-Flights and the Like, of which the following is a description, reference being had to the accompanying drawing, forming part of this specification.

My present invention relates to an improvement upon the invention heretofore patented to me in Letters Patent of the United States No. 601,429, dated March 29, 1898. Said patent discloses a method and apparatus for rolling strips of metal into spiral oonveyerflights and the like, consisting in passing a metal strip of substantially uniform thickness between a pair of cone-like pressure-rolls, so shaped and proportioned as to form between them a pass corresponding to a mathematical cross-section of the spiral to be produced.

' This method and apparatus I have put into extensive and highly successful practical use, producing large quantities of spiral conveyer flights for the market; but in the course of this manufacture I have discovered that it is not essential or even desirable that the tapering pass between the rolls through which the strip of metal is passed to convert it into a spiral shall correspond to a cross-section of the complete width of the spiral to be produced. On the contrary, I have found and satisfactorily determined by experiment and practical use of the apparatus that it is not essential that the base or thicker inner edge of the spiral shall be directly acted upon by and subjected to the pressure of the two cone-like rolls between which the strip is passed. In utilizing my presentimprovement, therefore, instead of shaping and proportioning the two rolls in such a way as to provide between them a pass corresponding to a cross-section of the complete width of the spiral to be produced I form between them a pass corresponding, for example, to three-fourths of the complete width of a cross-section of the spiral to be produced, measuring from the outer thinner edge toward the inner thicker edge or base of the spiral. When the strip of metal is passed between a pair of rolls of this improved form,

about one-fourth of its width atone edge will consequently project beyond the wider end of the pass (the working portion of the pass) between the rolls, so that the latter will not bear directly upon this portion of the strip at all. i

The action of the rolls upon the remainder of the width of the strip will serve to convert the strip into a spiral, the projecting edge or base of the strip being upset or bent upon itself, as it were, by the action of the rolls upon the remaining portion of the strip as the latter passes between them and is converted into spiral form.

Bearing in mind the foregoing statement, and referring also to my prior patent, my present improvement will be readily understood from the diagram shown in the accompanying drawing, in which the figure represents the working portions of a pair of pressure-rolls adapted for the practice of my method.

According to my prior patent aforesaid, the working portion of the pass between the two rolls extends the full width of the cross-section of the spiral, while in the present instance, as seen in the drawing, the rolls A B are offset or ground away at thewider end of the pass from the points a (0, thus leaving the thicker edge or base of the spiral E projecting some distance beyond the working portion of the pass. a, the portion along which the faces of the rolls exert a direct pressure upon the strip of metal passed between them. Instead of grinding away the rolls A B from the points a a, as in the drawing, their apices may be cut squarely off transversely of their axes at the points a a with substantially the same result, thus leaving the base of the strip to project entirely beyond the ends of the rolls.

In the practical use of the apparatus of my said prior patent I have found that there is considerable slippage between the faces of the rolls and surfaces of the strip of metal at the wider end of the pass, evidenced by the polished and worn appearance of the rolls at this point and contrasting with their appearance along the remainder of the pass. This slippage between the rolls and metal strip necessarily requires the overcoming of considerable friction between the rolls and the strip at the expense of the power of the machine, and I have found that by employing my improved rolls, in which I eliminate the portion of the pass at which this friction and slippage occur, much less power is required in the machine to convert a strip of given width and thickness into a corresponding spiral, and in this respect, therefore, my improvement both lessens the wear upon the rolls (which is in any event severe) and lessens the power required for operating the machine.

It will be understood that in preparing the rolls, as seen in the drawing, for the practice of my new method the shape of the pass will be determined by the shape of the cross-section of the spiral to be produced in the manner explained in my prior patent or in any other suitable manner and the rolls be then ground to shape to produce a pass between them corresponding to the cross-section of such spiral, less a portion of its width at its thicker edge or base, such portion being preferably about one-fourth of the complete width of the strip, but Variable more or less from that proportion.

Having thus fully described my invention, I claim The herein-described method of producing continuous strip spiral conveyer-flights and the like, consisting in passing a strip of metal of substantially uniform thickness between a pair of conelike pressure-rolls shaped and proportioned to form between them a tapering pass corresponding to a mathematical cross-section of a portion less than the complete width of the spiral to be produced, leaving the edge of the strip to project beyond the working portion of the pass at its Wider end, whereby such projecting portion of the strip remains out of pressure contact With the surfaces of the rolls but is transformed into spiral shape by the action of the rolls upon the remaining portion of the Width of the strip, substantially as described.

FRANK G. CALDl/VELL. Witnesses:

EDWARD Rno'ron, BEssIE SHADBoL'r. 

